I soppose:
1 - Rmagick eats a lot of memory
and 2 - FCGI (or DH policies) kill the process to protect the others users of the shared server.

I do:
- make an RoR application to upload images. A simple model with post and many images.
- create a new domain user and assign this application.
- freeze gems
- change .htaccess[1] and fcgi distpacher[2]
- deploy an aplication with svn and capistrano.

Solutions:
- Drop out Rmagick and install other gem for image manipulation. ImageScience for example. But Rmagick is the most complete tool.
- Extend my account to http://www.dreamhostps.com/ with >200MB of RAM.
- Find other job where they do not have technology involved such as goats keeper [joke]

Question:
Someone could successfully implement an application to upload images?